The peptide neurohormone, oxytocin plays a critical role in the regulation of a number of diverse central nervous system functions, which are highly relevant to schizophrenia. Several studies using animal models of psychosis indicate that oxytocin produces antipsychotic-like effects. A recent, small, proof-of-concept study, found that schizophrenia subjects taking intranasal oxytocin (40 IU BID) as an adjunct to existing antipsychotic drugs for 3 weeks had significantly reduced symptoms of psychosis and improved memory compared to subjects taking placebo. We now propose to perform a follow-up study adding a higher dose and increasing the duration of treatment with the goal of replicating and extending the promising preliminary findings. Specifically, the proposed study will test the efficacy and safety of 6-weeks of daily intranasal oxytocin (40 IU BID or 80 IU BID compared to placebo on core symptoms of schizophrenia and on cognitive deficits associated with the disorder. It is hypothesized that both oxytocin doses will improve symptoms and cognitive function with the higher dose (80 IU BID) producing stronger effects. The proposed study will provide critical efficacy, dosing and safety information regarding the feasibility of developing oxytocin as a treatment for schizophrenia. PUBLIC HEALTH RELEVANCE: Schizophrenia is a debilitating disorder for which current treatments are unsatisfactory. We propose a study aimed at investigating the effectiveness of the hormone oxytocin as an add-on to conventional schizophrenia treatment. The proposed experiment may help lead to superior treatments for this illness.